The present invention relates to trailers for loading and transporting farm implements, construction equipment and other wheeled and tracked equipment and, more particularly, to a trailer of the type wherein the trailer support bed can be lowered or inclined from its normal load transporting height to a lower level or different inclination for loading and unloading.
A search of the prior art failed to uncover any prior art reference which discloses the equipment trailer of the present invention. A number of prior art patents were uncovered which disclose a variety of equipment trailers having depressible, tiltable or otherwise shiftable beds to facilitate loading and unloading of heavy equipment. The following is a listing of the prior art U.S. patents uncovered during the aforementioned search: U.S. Pat. Nos. 2,611,583; 2,743,936; 2,885,216; 3,003,780; 3,199,889; 3,214,047; 3,239,274; 3,380,607; 3,838,868; 3,901,398; 4,040,643; 4,101,158; 4,119,224; 4,125,198.
Typical of the trailer apparatus heretofore known and used for transporting equipment are the trailers disclosed, for example, in the above-listed U.S. Pat. Nos. 3,214,047 and 4,125,198. These trailers are provided with tiltable beds wherein the trailer bed is pivoted or otherwise shifted to a position such that one end of the trailer bed bears against the ground to facilitate driving the equipment to be transported up the inclined trailer bed.
In the case of the trailer disclosed in U.S. Pat. No. 3,214,047, the trailer bed is carried centrally on two pair of wheels, i.e., tandem wheels, and is pivoted about a horizontal axis midway between the tandem wheel pairs so that the rear end of the bed bears against the ground for loading. The pivot axis of the trailer bed is preferably arranged as low to the ground as possible to minimize the angle of inclination of the bed and assure ease of loading and maintenance of a low center of gravity of the load.
U.S. Pat. No. 4,125,198 discloses a trailer bed having an undercarriage which is mounted for reciprocal fore-and-aft movement. A lifting mechanism, such as a hydraulic cylinder, is provided at the forward end of the trailer bed for raising such end until the rear end of the trailer bed comes into contact with the ground so as to provide an incline for loading equipment onto the trailer bed.
Thus, one of the prior art approaches to loading equipment trailers has involved pivoting or otherwise tilting the trailer so that one end thereof bears upon the ground to provide an inclined loading ramp. Improvements to this approach have involved measures to reduce the angle of inclination of the trailer bed to facilitate loading and improve the safety and stability characteristics of the trailer.